/*
 * demand.c - Support routines for demand-dialling.
 *
 * Copyright (c) 1996-2002 Paul Mackerras. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. The name(s) of the authors of this software must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission.
 *
 * 3. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Paul Mackerras
 *     <paulus@samba.org>".
 *
 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "netif/ppp/ppp_opts.h"
#if PPP_SUPPORT && DEMAND_SUPPORT  /* don't build if not configured for use in lwipopts.h */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <unistd.h>
#include <syslog.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#ifdef PPP_FILTER
	#include <pcap-bpf.h>
#endif

#include "netif/ppp/ppp_impl.h"

#include "netif/ppp/fsm.h"
#include "netif/ppp/ipcp.h"
#include "netif/ppp/lcp.h"

char* frame;
int framelen;
int framemax;
int escape_flag;
int flush_flag;
int fcs;

struct packet {
	int length;
	struct packet* next;
	unsigned char data[1];
};

struct packet* pend_q;
struct packet* pend_qtail;

static int active_packet(unsigned char*, int);

/*
 * demand_conf - configure the interface for doing dial-on-demand.
 */
void
demand_conf()
{
	int i;
	const struct protent* protp;

	/*    framemax = lcp_allowoptions[0].mru;
	    if (framemax < PPP_MRU) */
	framemax = PPP_MRU;
	framemax += PPP_HDRLEN + PPP_FCSLEN;
	frame = malloc(framemax);

	if(frame == NULL)
		novm("demand frame");

	framelen = 0;
	pend_q = NULL;
	escape_flag = 0;
	flush_flag = 0;
	fcs = PPP_INITFCS;

	netif_set_mtu(pcb, LWIP_MIN(lcp_allowoptions[0].mru, PPP_MRU));

	if(ppp_send_config(pcb, PPP_MRU, (u32_t) 0, 0, 0) < 0
	        || ppp_recv_config(pcb, PPP_MRU, (u32_t) 0, 0, 0) < 0)
		fatal("Couldn't set up demand-dialled PPP interface: %m");

#ifdef PPP_FILTER
	set_filters(&pass_filter, &active_filter);
#endif

	/*
	 * Call the demand_conf procedure for each protocol that's got one.
	 */
	for(i = 0; (protp = protocols[i]) != NULL; ++i)
		if(protp->demand_conf != NULL)
			((*protp->demand_conf)(pcb));

	/* FIXME: find a way to die() here */
#if 0

	if(!((*protp->demand_conf)(pcb)))
		die(1);

#endif
}


/*
 * demand_block - set each network protocol to block further packets.
 */
void
demand_block()
{
	int i;
	const struct protent* protp;

	for(i = 0; (protp = protocols[i]) != NULL; ++i)
		if(protp->demand_conf != NULL)
			sifnpmode(pcb, protp->protocol & ~0x8000, NPMODE_QUEUE);

	get_loop_output();
}

/*
 * demand_discard - set each network protocol to discard packets
 * with an error.
 */
void
demand_discard()
{
	struct packet* pkt, *nextpkt;
	int i;
	const struct protent* protp;

	for(i = 0; (protp = protocols[i]) != NULL; ++i)
		if(protp->demand_conf != NULL)
			sifnpmode(pcb, protp->protocol & ~0x8000, NPMODE_ERROR);

	get_loop_output();

	/* discard all saved packets */
	for(pkt = pend_q; pkt != NULL; pkt = nextpkt) {
		nextpkt = pkt->next;
		free(pkt);
	}

	pend_q = NULL;
	framelen = 0;
	flush_flag = 0;
	escape_flag = 0;
	fcs = PPP_INITFCS;
}

/*
 * demand_unblock - set each enabled network protocol to pass packets.
 */
void
demand_unblock()
{
	int i;
	const struct protent* protp;

	for(i = 0; (protp = protocols[i]) != NULL; ++i)
		if(protp->demand_conf != NULL)
			sifnpmode(pcb, protp->protocol & ~0x8000, NPMODE_PASS);
}

/*
 * FCS lookup table as calculated by genfcstab.
 */
static u_short fcstab[256] = {
	0x0000,	0x1189,	0x2312,	0x329b,	0x4624,	0x57ad,	0x6536,	0x74bf,
	0x8c48,	0x9dc1,	0xaf5a,	0xbed3,	0xca6c,	0xdbe5,	0xe97e,	0xf8f7,
	0x1081,	0x0108,	0x3393,	0x221a,	0x56a5,	0x472c,	0x75b7,	0x643e,
	0x9cc9,	0x8d40,	0xbfdb,	0xae52,	0xdaed,	0xcb64,	0xf9ff,	0xe876,
	0x2102,	0x308b,	0x0210,	0x1399,	0x6726,	0x76af,	0x4434,	0x55bd,
	0xad4a,	0xbcc3,	0x8e58,	0x9fd1,	0xeb6e,	0xfae7,	0xc87c,	0xd9f5,
	0x3183,	0x200a,	0x1291,	0x0318,	0x77a7,	0x662e,	0x54b5,	0x453c,
	0xbdcb,	0xac42,	0x9ed9,	0x8f50,	0xfbef,	0xea66,	0xd8fd,	0xc974,
	0x4204,	0x538d,	0x6116,	0x709f,	0x0420,	0x15a9,	0x2732,	0x36bb,
	0xce4c,	0xdfc5,	0xed5e,	0xfcd7,	0x8868,	0x99e1,	0xab7a,	0xbaf3,
	0x5285,	0x430c,	0x7197,	0x601e,	0x14a1,	0x0528,	0x37b3,	0x263a,
	0xdecd,	0xcf44,	0xfddf,	0xec56,	0x98e9,	0x8960,	0xbbfb,	0xaa72,
	0x6306,	0x728f,	0x4014,	0x519d,	0x2522,	0x34ab,	0x0630,	0x17b9,
	0xef4e,	0xfec7,	0xcc5c,	0xddd5,	0xa96a,	0xb8e3,	0x8a78,	0x9bf1,
	0x7387,	0x620e,	0x5095,	0x411c,	0x35a3,	0x242a,	0x16b1,	0x0738,
	0xffcf,	0xee46,	0xdcdd,	0xcd54,	0xb9eb,	0xa862,	0x9af9,	0x8b70,
	0x8408,	0x9581,	0xa71a,	0xb693,	0xc22c,	0xd3a5,	0xe13e,	0xf0b7,
	0x0840,	0x19c9,	0x2b52,	0x3adb,	0x4e64,	0x5fed,	0x6d76,	0x7cff,
	0x9489,	0x8500,	0xb79b,	0xa612,	0xd2ad,	0xc324,	0xf1bf,	0xe036,
	0x18c1,	0x0948,	0x3bd3,	0x2a5a,	0x5ee5,	0x4f6c,	0x7df7,	0x6c7e,
	0xa50a,	0xb483,	0x8618,	0x9791,	0xe32e,	0xf2a7,	0xc03c,	0xd1b5,
	0x2942,	0x38cb,	0x0a50,	0x1bd9,	0x6f66,	0x7eef,	0x4c74,	0x5dfd,
	0xb58b,	0xa402,	0x9699,	0x8710,	0xf3af,	0xe226,	0xd0bd,	0xc134,
	0x39c3,	0x284a,	0x1ad1,	0x0b58,	0x7fe7,	0x6e6e,	0x5cf5,	0x4d7c,
	0xc60c,	0xd785,	0xe51e,	0xf497,	0x8028,	0x91a1,	0xa33a,	0xb2b3,
	0x4a44,	0x5bcd,	0x6956,	0x78df,	0x0c60,	0x1de9,	0x2f72,	0x3efb,
	0xd68d,	0xc704,	0xf59f,	0xe416,	0x90a9,	0x8120,	0xb3bb,	0xa232,
	0x5ac5,	0x4b4c,	0x79d7,	0x685e,	0x1ce1,	0x0d68,	0x3ff3,	0x2e7a,
	0xe70e,	0xf687,	0xc41c,	0xd595,	0xa12a,	0xb0a3,	0x8238,	0x93b1,
	0x6b46,	0x7acf,	0x4854,	0x59dd,	0x2d62,	0x3ceb,	0x0e70,	0x1ff9,
	0xf78f,	0xe606,	0xd49d,	0xc514,	0xb1ab,	0xa022,	0x92b9,	0x8330,
	0x7bc7,	0x6a4e,	0x58d5,	0x495c,	0x3de3,	0x2c6a,	0x1ef1,	0x0f78
};

/*
 * loop_chars - process characters received from the loopback.
 * Calls loop_frame when a complete frame has been accumulated.
 * Return value is 1 if we need to bring up the link, 0 otherwise.
 */
int
loop_chars(p, n)
unsigned char* p;
int n;
{
	int c, rv;

	rv = 0;

	/* check for synchronous connection... */

	if((p[0] == 0xFF) && (p[1] == 0x03)) {
		rv = loop_frame(p, n);
		return rv;
	}

	for(; n > 0; --n) {
		c = *p++;

		if(c == PPP_FLAG) {
			if(!escape_flag && !flush_flag
			        && framelen > 2 && fcs == PPP_GOODFCS) {
				framelen -= 2;

				if(loop_frame((unsigned char*)frame, framelen))
					rv = 1;
			}

			framelen = 0;
			flush_flag = 0;
			escape_flag = 0;
			fcs = PPP_INITFCS;
			continue;
		}

		if(flush_flag)
			continue;

		if(escape_flag) {
			c ^= PPP_TRANS;
			escape_flag = 0;
		} else if(c == PPP_ESCAPE) {
			escape_flag = 1;
			continue;
		}

		if(framelen >= framemax) {
			flush_flag = 1;
			continue;
		}

		frame[framelen++] = c;
		fcs = PPP_FCS(fcs, c);
	}

	return rv;
}

/*
 * loop_frame - given a frame obtained from the loopback,
 * decide whether to bring up the link or not, and, if we want
 * to transmit this frame later, put it on the pending queue.
 * Return value is 1 if we need to bring up the link, 0 otherwise.
 * We assume that the kernel driver has already applied the
 * pass_filter, so we won't get packets it rejected.
 * We apply the active_filter to see if we want this packet to
 * bring up the link.
 */
int
loop_frame(frame, len)
unsigned char* frame;
int len;
{
	struct packet* pkt;

	/* dbglog("from loop: %P", frame, len); */
	if(len < PPP_HDRLEN)
		return 0;

	if((PPP_PROTOCOL(frame) & 0x8000) != 0)
		return 0;		/* shouldn't get any of these anyway */

	if(!active_packet(frame, len))
		return 0;

	pkt = (struct packet*) malloc(sizeof(struct packet) + len);

	if(pkt != NULL) {
		pkt->length = len;
		pkt->next = NULL;
		memcpy(pkt->data, frame, len);

		if(pend_q == NULL)
			pend_q = pkt;
		else
			pend_qtail->next = pkt;

		pend_qtail = pkt;
	}

	return 1;
}

/*
 * demand_rexmit - Resend all those frames which we got via the
 * loopback, now that the real serial link is up.
 */
void
demand_rexmit(proto, newip)
int proto;
u32_t newip;
{
	struct packet* pkt, *prev, *nextpkt;
	unsigned short checksum;
	unsigned short pkt_checksum = 0;
	unsigned iphdr;
	struct timeval tv;
	char cv = 0;
	char ipstr[16];

	prev = NULL;
	pkt = pend_q;
	pend_q = NULL;
	tv.tv_sec = 1;
	tv.tv_usec = 0;
	select(0, NULL, NULL, NULL, &tv);	/* Sleep for 1 Seconds */

	for(; pkt != NULL; pkt = nextpkt) {
		nextpkt = pkt->next;

		if(PPP_PROTOCOL(pkt->data) == proto) {
			if((proto == PPP_IP) && newip) {
				/* Get old checksum */

				iphdr = (pkt->data[4] & 15) << 2;
				checksum = *((unsigned short*)(pkt->data + 14));

				if(checksum == 0xFFFF) {
					checksum = 0;
				}


				if(pkt->data[13] == 17) {
					pkt_checksum =  *((unsigned short*)(pkt->data + 10 + iphdr));

					if(pkt_checksum) {
						cv = 1;

						if(pkt_checksum == 0xFFFF) {
							pkt_checksum = 0;
						}
					} else {
						cv = 0;
					}
				}

				if(pkt->data[13] == 6) {
					pkt_checksum = *((unsigned short*)(pkt->data + 20 + iphdr));
					cv = 1;

					if(pkt_checksum == 0xFFFF) {
						pkt_checksum = 0;
					}
				}

				/* Delete old Source-IP-Address */
				checksum -= *((unsigned short*)(pkt->data + 16)) ^ 0xFFFF;
				checksum -= *((unsigned short*)(pkt->data + 18)) ^ 0xFFFF;

				pkt_checksum -= *((unsigned short*)(pkt->data + 16)) ^ 0xFFFF;
				pkt_checksum -= *((unsigned short*)(pkt->data + 18)) ^ 0xFFFF;

				/* Change Source-IP-Address */
				* ((u32_t*)(pkt->data + 16)) = newip;

				/* Add new Source-IP-Address */
				checksum += *((unsigned short*)(pkt->data + 16)) ^ 0xFFFF;
				checksum += *((unsigned short*)(pkt->data + 18)) ^ 0xFFFF;

				pkt_checksum += *((unsigned short*)(pkt->data + 16)) ^ 0xFFFF;
				pkt_checksum += *((unsigned short*)(pkt->data + 18)) ^ 0xFFFF;

				/* Write new checksum */
				if(!checksum) {
					checksum = 0xFFFF;
				}

				*((unsigned short*)(pkt->data + 14)) = checksum;

				if(pkt->data[13] == 6) {
					*((unsigned short*)(pkt->data + 20 + iphdr)) = pkt_checksum;
				}

				if(cv && (pkt->data[13] == 17)) {
					*((unsigned short*)(pkt->data + 10 + iphdr)) = pkt_checksum;
				}

				/* Log Packet */
				strcpy(ipstr, inet_ntoa(*((struct in_addr*)(pkt->data + 16))));

				if(pkt->data[13] == 1) {
					syslog(LOG_INFO, "Open ICMP %s -> %s\n",
					       ipstr,
					       inet_ntoa(*((struct in_addr*)(pkt->data + 20))));
				} else {
					syslog(LOG_INFO, "Open %s %s:%d -> %s:%d\n",
					       pkt->data[13] == 6 ? "TCP" : "UDP",
					       ipstr,
					       ntohs(*((short*)(pkt->data + iphdr + 4))),
					       inet_ntoa(*((struct in_addr*)(pkt->data + 20))),
					       ntohs(*((short*)(pkt->data + iphdr + 6))));
				}
			}

			output(pcb, pkt->data, pkt->length);
			free(pkt);
		} else {
			if(prev == NULL)
				pend_q = pkt;
			else
				prev->next = pkt;

			prev = pkt;
		}
	}

	pend_qtail = prev;

	if(prev != NULL)
		prev->next = NULL;
}

/*
 * Scan a packet to decide whether it is an "active" packet,
 * that is, whether it is worth bringing up the link for.
 */
static int
active_packet(p, len)
unsigned char* p;
int len;
{
	int proto, i;
	const struct protent* protp;

	if(len < PPP_HDRLEN)
		return 0;

	proto = PPP_PROTOCOL(p);
#ifdef PPP_FILTER
	p[0] = 1;		/* outbound packet indicator */

	if((pass_filter.bf_len != 0
	        && bpf_filter(pass_filter.bf_insns, p, len, len) == 0)
	        || (active_filter.bf_len != 0
	            && bpf_filter(active_filter.bf_insns, p, len, len) == 0)) {
		p[0] = 0xff;
		return 0;
	}

	p[0] = 0xff;
#endif

	for(i = 0; (protp = protocols[i]) != NULL; ++i) {
		if(protp->protocol < 0xC000 && (protp->protocol & ~0x8000) == proto) {
			if(protp->active_pkt == NULL)
				return 1;

			return (*protp->active_pkt)(p, len);
		}
	}

	return 0;			/* not a supported protocol !!?? */
}

#endif /* PPP_SUPPORT && DEMAND_SUPPORT */
